# environments

Rsbuild supports building outputs for multiple environments. You can use `environments` to define different Rsbuild configurations for each environment.

> Please refer to [Multi-environment builds](/guide/advanced/environments) for more information.

- **Type:**

```ts
interface EnvironmentConfig {
  plugins?: RsbuildPlugins;
  dev?: Pick<
    DevConfig,
    'hmr' | 'assetPrefix' | 'progressBar' | 'lazyCompilation' | 'writeToDisk'
  >;
  html?: HtmlConfig;
  tools?: ToolsConfig;
  source?: SourceConfig;
  output?: OutputConfig;
  resolve?: ResolveConfig;
  security?: SecurityConfig;
  performance?: PerformanceConfig;
  moduleFederation?: ModuleFederationConfig;
}

type Environments = {
  [name: string]: EnvironmentConfig;
};
```

- **Default:** `undefined`

:::tip
`environments` does not support configuring `server` options and some `dev` options, because multiple environments share the same server instance.
:::

## Example

Configure Rsbuild configuration for `web` (client) and `node` (SSR) environments:

```ts title="rsbuild.config.ts"
export default {
  // Shared configuration for all environments
  resolve: {
    alias: {
      '@common': './src/common',
    },
  },
  environments: {
    // configuration for client
    web: {
      source: {
        entry: {
          index: './src/index.client.js',
        },
      },
      output: {
        target: 'web',
      },
      resolve: {
        alias: {
          '@common1': './src/web/common1',
        },
      },
    },
    // configuration for SSR
    node: {
      source: {
        entry: {
          index: './src/index.server.js',
        },
      },
      output: {
        target: 'node',
      },
      resolve: {
        alias: {
          '@common1': './src/ssr/common1',
        },
      },
    },
  },
};
```

For the `web` environment, the merged Rsbuild configuration is:

```js
const webConfig = {
  source: {
    entry: {
      index: './src/index.client.js',
    },
  },
  output: {
    target: 'web',
  },
  resolve: {
    alias: {
      '@common': './src/common',
      '@common1': './src/web/common1',
    },
  },
};
```

For the `node` environment, the merged Rsbuild configuration is:

```js
const nodeConfig = {
  source: {
    entry: {
      index: './src/index.server.js',
    },
  },
  output: {
    target: 'node',
  },
  resolve: {
    alias: {
      '@common': './src/common',
      '@common1': './src/ssr/common1',
    },
  },
};
```

## Environment name

Since environment names are used for directory names and object property names, it is recommended to only include letters, numbers, `-`, `_`, and `$`. When using other characters, Rsbuild will output a warning to prompt you.

```ts
export default {
  environments: {
    someName: {}, // ✅
    some_name: {}, // ✅
    'some-name': {}, // ✅
    'some:name': {}, // ❌
  },
};
```
